South Korea's government is refusing to suspend its seasonal flu vaccination effort, despite growing calls for a halt after the deaths of at least 13 of those vaccinated.
The government says it's found no direct link between the deaths and vaccines.
But the Korean Medical Association - an influential group of doctors - urged the government to halt inoculation programs for now, in a bid to alleviate public concerns and ensure the vaccines were safe.
Kim Chong-in, leader of the main opposition People Power party, also wants the program halted until the causes of the deaths were verified.
The Korea Disease Control and Prevention Agency says that at least 11 of the 13 dead - including a 17-year-old boy - were part of a campaign to immunize 19 million teenagers and senior citizens for free.
South Korea ordered a fifth more flu vaccines this year to ward off what it calls a "twindemic," or the prospect that people with flu develop coronavirus complications and overburden hospitals in winter.
The free program has proved controversial since it began last month. The launch had been suspended for three weeks after the discovery that about 5 million doses were kept at room temperature rather than being refrigerated, as required.
Officials said 8.3 million people had been inoculated since the program resumed last week - with only about 350 adverse reactions reported.